As to a traditional parallel-type LED light string, positive and negative electrodes of a power supply both are connected to the first LED unit of the light string, because of the problem of voltage drop, the LED unit at the front of the light string and near power supply wires are relatively bright, the more backward in position of the LED unit, the darker the LED unit is, and when the number of the LED unit is more than 30, the brightnesses at the front and at the rear of the light string will be very different. If a supply voltage is attempted to be increased for the purpose of solving the problem of voltage drop, the LED unit at the most front of the light string will be burned out soon.
In another aspect, a “DCTD-protocol based LED” is also called as a “LED equipped with IC chip” and may be a monochromatic LED equipped with IC chip, a RGB LED equipped with IC chip or a W+RGB LED equipped with IC chip.